The present invention relates generally to rotary fluid displacement apparatus such as pumps, motors, or combination motor-pumps or metering devices, and particularly to improvements to such rotary fluid displacement apparatus which increase product life and efficiency.
The most important interface between parts in a rotor stack assembly of a rotary fluid displacement apparatus with an orbiting toothed ring member occurs between the valve discs including the fluid passages and the elements including the fluid transfer passageways. This interface is crucial because it can affect timing and efficiency and is where the largest wear problems occur. Specifically, the valve discs formed of torlon tend to wear into the elements typically formed of zinc and including the fluid transfer passageways. In addition to affecting the valving operation, such wear causes the rotor stack assembly to loosen which may accelerate wear in other parts. Also, the elements including the fluid transfer passageways tend to wear away in very fine grains which spread throughout the apparatus. The lubrication for the many moving parts inside the casing of prior rotary fluid displacement apparatus mixed with the zinc particles to form a slurry which was very abrasive to other moving parts of the apparatus.
Also, the casing can play a significant role in the life and performance of the apparatus. Specifically, if a perfect seal is not achieved between casing parts, oil and air are allowed to leak, the effects of which are recognizable in both efficiency and aesthetics. Prior casings of rotary fluid displacement apparatus were formed from multiple parts which often promoted air leaks because of the mere number of potential leak paths, the difficulty of sealing, and the type of seals required. Prior casings were difficult and expensive to manufacture and assemble with high repeatability, were prone to wear, and tended to accentuate the noise and vibration problems inherent in an eccentric drive.
Thus, a need exists for an improved rotary fluid displacement apparatus with an orbiting toothed ring member which overcomes the problems and shortcomings of prior apparatus.